Technical Field
The invention generally relate to a machining device, such as a cutting device that may include a circular blade rotatably driven for performing a cutting operation or a grooving operation of a workpiece, such as an aluminum workpiece, by a predetermined depth.
Related Art
Japanese Laid-Open Patent Publication No. 2000-073310 (JP-A-2000-073310) discloses a technique for reducing noise that may be generated by the rotation of a blade of a cutting device that may be used for cutting a concrete floor surface and an asphalt road surface.
However, in a structure for covering the blade disclosed in the above publication, a polyurethane resin material is disposed in a sound adsorbing space formed around the blade. This arrangement may lead to an increase in a manufacturing cost of the cutting device. Other than cutting devices of a type disclose in the publication, blade covers (called “blade cases”) have been generally incorporated for covering blades of various machining devices, such as a grooving device, a portable circular saw and a miter saw. Also for these machining devices, there has been a problem of generation of unpleasant sound, such as sound of “pea.” It has been considered that such noise or abnormal sound may be generated when the frequency of air vibration generated by the rotation of the blade at a specific rotational speed within the cover becomes to a value equal to or near a natural system frequency determined by various factors, such as the weight of the blade, the shape of the cover, etc.
In view of the above, there is a need in the art for a technique of reducing nose or abnormal sound generated by the rotation of a blade within a blade cover of a machining device, without leading to a substantial increase in a manufacturing cost of the machining device.